FIG. 1 is a block diagram showing an arrangement of a telephone system as disclosed in Japanese Patent Application Laid-Open No. 98575/1999. In the figure, reference numeral 1 denotes a mobile terminal, and reference numeral 2 denotes a mobile phone network inclusive of a base station or the like which performs transmission and reception of radio signals to and from the mobile terminal 1.
In the mobile terminal 1, reference numeral 11 denotes a wireless section for performing transmission and reception of radio signals to and from the mobile phone network 2. Reference numeral 12 denotes an operating section for processing inputs from a microphone 13, outputs to a loud speaker 14, and inputs from keys 15 for entering various setting inputs. Reference numeral 16 denotes a control section that controls transmission and reception in wireless communications and also controls reception of voices through the microphone 13, driving of the loud speaker 14, inputting through the keys 15 or the like. Reference numeral 17 denotes a moving-speed detecting section for detecting a moving speed of a mobile body such as an automotive vehicle which has mounted on board the mobile terminal 1.
A description will now be made about the operation.
If the moving-speed of the mobile body which is detected by the moving-speed detecting section 17 has exceeded a predetermined value and if this state continues for a predetermined period of time or more, the transmitting function of the wireless section 11 is stopped. If the detected moving speed has fallen to the level below a predetermined value and this state continues for a predetermined period of time or more, the stoppage of the transmitting function of the wireless section 11 is released. Further, in a state in which the transmitting function is stopped, communication is performed through a second communicating means such as paging service function, automatic answering telephone service, short mail service, call reception transfer service and so on.
As a method for the moving-speed detecting section 17 to detect the moving speed, there is, for example, a method as disclosed in Japanese Patent Application Laid-Open No. 215053/1999 in which the moving speed is estimated by a change in the transmitting power, or a method as disclosed in Japanese Patent Application Laid-Open No. 149550/1996 in which a fading pitch (period) of a standby receiving channel is detected.
In this manner, by determining whether or not the mobile body is moving based on the duration time of its moving speed above a predetermined value, the transmitting function is stopped, and the communication means is automatically switched to the second communicating means. Therefore, in the case where the mobile terminal 1 receives a call, the user of the mobile terminal 1 cannot determine as to whether or not the call is of an urgent nature in a state in which the switching has already been changed to the second communicating means. Due to this, the user of the mobile terminal 1 will not start to take a voluntary action to enable him or her to commence the conversation in reply to the received call, for example, when driving an automotive vehicle, by parking it on the roadside so that the moving speed becomes lower than a predetermined value and holding the value for a predetermined period of time.
In this case, the message from the caller will be received by the above-described second communicating means. However, since the user of the mobile terminal 1 would not necessarily take an i immediate action to check this message for the above-described reason, the confirmation of the contents of the message is sometimes delayed or the received message itself would be left forgotten.
Further, even in the case where a return reply to the caller is required, the user of the mobile terminal 1 may sometimes forget the necessity to do so. In this manner, the caller will have to call again thereafter on the assumption that the called party might have forgotten to confirm the message or might have forgotten to reply by return call.
Since the conventional telephone system is arranged as described above, there is such a problem that despite the state in which the telephone system itself is capable of providing communications, it cannot surely perform the conversation as soon as possible on an emergency case or the like.
This invention has been made to solve the forgoing problems, and it is an object of the present invention to provide a telephone system which enables, in a state in which the telephone system itself is capable of providing a conversation connection but is incapable of conversation because the mobile terminal is moving, the user of the mobile terminal 1 to take a voluntary action to make a conversation even without executing a repeated calling on the part of the caller; and which enables the user, when the mobile terminal 1 has come to a state in which a secure communication is enabled, to quickly and securely perform the conversation with the caller.